Liquid and meltable solid grades of scorch protected peroxides

ABSTRACT

Embodiments of organic peroxide formulations provide longer scorch time protection and require fewer additives. The peroxide formulations may include, for example, at least one organic peroxide, at least one nitroxide-containing compound (e.g., 4-hydroxy-TEMPO), and at least one quinone-containing compound (e.g., mono-tert-butylhydroquinone).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 15/531,740, filedMay 31, 2017, which is a national stage application under 35 U.S.C. §371 of PCT/US2015/063854 filed Dec. 4, 2015, which claims benefit toU.S. patent application Ser. No. 62/089,384, filed Dec. 9, 2014.

FIELD OF THE INVENTION

The present invention relates to compositions and methods for creatingliquid or meltable solid peroxide formulations with increased scorchprotection, and products made by those methods.

BACKGROUND OF THE INVENTION

Organic peroxides are commonly used to crosslink thermoplastic polymersand elastomers, and their mixtures, when the final products are requiredto meet high mechanical and physical requirements, such as improvedthermal aging and lower residual (permanent) deformation under pressurecompared with uncrosslinked thermoplastics and/or sulfur curedelastomers. Since both thermoplastics and elastomers are solid materialsat room temperatures, in order to add the free radical crosslinkingagent and any other desired ingredients such as dyes, pigments, fillers,antioxidants, UV and heat stabilizers and the like into the polymer, thepolymers must be mechanically mixed with the free radical crosslinkingagent and any of the other desired ingredients at temperaturessufficiently elevated to allow the polymers to flow in the mixingequipment.

The crosslinking period and the time from the addition of the freeradical precursor up to incipient cross linkage (scorch time) aredependent on the thermal decomposition rate (conveniently expressed asthe half-life period) of the free radical initiators employed ascrosslinking agents. The longer the processing time before onset ofscorch that can be provided to a manufacturer without sacrifice of finalcrosslink speed or density, the more beneficial it will be because withconventional methods of mixing or compounding, such as milling, Banbury,or extrusion, scorch begins when the time and temperature relationshipresults in the start of appreciable decomposition of the free radicalinitiator. If this occurs too soon, gel particles in the mass of polymerto be compounded may be formed thereby producing non-homogeneity in thefinal product. Excessive scorch reduces the plastic properties of thematerial so that it can no longer be processed, thus, resulting in lossof the entire batch.

There have been several attempts to extend scorch time. U.S. Pat. No.5,245,084 discloses the use of organic peroxides suitable forcrosslinking thermoplastics and elastomers in combination with aspecific group of hydroquinones and a crosslinkage promoter selectedfrom crosslinkage promoters normally used in these applications. U.S.Pat. No. 6,197,231 teaches the use of a combination of free radicalinitiators (either organic peroxides or a specific class of azoinitiators) in combination with hydroquinones, crosslinkage promotersand known sulfur releasing sulfur accelerators for extending scorch timewithout adverse effects on cure time or cure density for thermoplastics,elastomers and their mixtures.

There are several commercial grades of extended organic peroxideformulations on fillers. However, due to the poor solubility of solidadditives in organic peroxides, it has not been possible to create aliquid peroxide formulation or homogeneous meltable solid that providessufficient scorch protection and contains either no filler or loweramounts of filler. It would be desirable to have organic peroxideformulations with longer scorch times and lower loadings of additives.

SUMMARY OF THE INVENTION

Embodiments of the present invention relate to organic peroxidecompositions comprising scorch retarders. Embodiments of the inventionalso relate to crosslinkable elastomer compositions, processes forcuring the elastomers, and products made by such processes

The scorch retarders 4-hydroxy-TEMPO (4-OHT;4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl) andmono-tert-butylhydroquinone (MTBHQ) have very limited solubility inorganic peroxides. However, the applicants unexpectedly found that ablend of the two retarders (4-OHT and MTBHQ) provides longer scorch timewith less total additive needed in the organic peroxide formulation.This unexpected synergy, when using blends of these two classes ofcompounds, allows for easier dissolution of the additive package intothe peroxide because significantly less is required.

In accordance with embodiments of the present invention, homogeneousliquid and meltable solid peroxide formulations can be created withoutthe need for filler, or with very little filler. Furthermore, it ispossible to melt the peroxide formulations or spray the liquidformulations onto fillers, if such a form is desired.

Non-limiting examples of applications for the peroxide formulations ofthe present invention include the use of liquid and filler-extendedgrades of the organic peroxides for crosslinked HDPE rotational molding;PEX-a pipe production; injection molded, compression molded, transfermolded crosslinked goods; wire and cable; general crosslinkedelastomers, rubber and polymers; modification of polymer molecularweight and grafting of agents such as maleic anhydride (MAH) andglycidyl methacrylate; dynamic vulcanization for production of TPV(thermoplastic vulcanizates); and crosslinked rubber or polymer foams.

Embodiments of the present invention relate to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide, at least one nitroxide-containing compound(e.g., 4-OHT), and at least one quinone-containing compound (e.g.,MTBHQ). The formulation provides longer scorch time protection and lesstotal additive in comparison to prior art formulations.

Embodiments of the present invention also relate to an elastomercomposition comprising, consisting essentially of, or consisting of atleast one elastomer, at least one organic peroxide, at least onenitroxide-containing compound (e.g., 4-OHT), and at least onequinone-containing compound (e.g., MTBHQ).

Embodiments of the present invention also relate to a process for curingan elastomer composition, said process comprising, consistingessentially of, or consisting of curing an elastomer composition in thepresence of oxygen, wherein the elastomer composition comprises,consists essentially of, or consists of at least one elastomer, at leastone organic peroxide, at least one nitroxide-containing compound (e.g.,4-OHT), and at least one quinone-containing compound (e.g., MTBHQ).Embodiments of the present invention also relate to products made bythis process.

DETAILED DESCRIPTION

The applicants have discovered that a blend of at least onenitroxide-containing compound (e.g., 4-OHT) and at least onequinone-containing compound (e.g., MTBHQ) provides organic peroxideformulations with longer scorch times, wherein less total additive isneeded in the formulation. This unexpected synergy, when using blends ofthese two classes of compounds, allows for easier dissolution of theadditive package into the peroxide because significantly less isrequired.

One aspect of the present invention relates to an organic peroxideformulation comprising, consisting essentially of, or consisting of atleast one organic peroxide, at least one nitroxide-containing compound(e.g., 4-hydroxy-TEMPO (4-OHT)), and at least one quinone-containingcompound (e.g., mono-tert-butylhydroquinone (MTBHQ)). The formulationprovides longer scorch time protection and less total additive incomparison to prior art formulations

All those organic peroxides known to undergo decomposition by heat togenerate radicals capable of initiating the desired curing(crosslinking) reactions are contemplated as suitable for use in theformulations of the present invention. Non-limiting examples includedialkyl peroxides, diperoxyketals, mono-peroxy carbonates, cyclic ketoneperoxides, diacyl peroxides, organosulfonyl peroxides, peroxyesters andsolid, room temperature stable peroxydicarbonates. In at least oneembodiment, the organic peroxide is selected from dialkyl peroxides,peroxyketals, cyclic ketone peroxides, monoperoxycarbonates,peroxyesters and diacyl peroxides.

Peroxide names and physical properties for all these classes of organicperoxides can be found in “Organic Peroxides” by Jose Sanchez and TerryN. Myers; Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Ed.,Volume 18, (1996), the disclosure of which is incorporated herein byreference.

Illustrative dialkyl peroxide initiators include:

-   di-t-butyl peroxide;-   t-butyl cumyl peroxide;-   2,5-di(cumylperoxy)-2,5-dimethyl hexane;-   2,5-di(cumylperoxy)-2,5-dimethyl hexyne-3;-   4-methyl-4-(t-butylperoxy)-2-pentanol;-   4-methyl-4-(t-amylperoxy)-2-pentanol;-   4-methyl-4-(cumylperoxy)-2-pentanol;-   4-methyl-4-(t-butylperoxy)-2-pentanone;-   4-methyl-4-(t-amylperoxy)-2-pentanone;-   4-methyl-4-(cumylperoxy)-2-pentanone;-   2,5-dimethyl-2,5-di(t-butylperoxy)hexane;-   2,5-dimethyl-2,5-di(t-amylperoxy)hexane;-   2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;-   2,5-dimethyl-2,5-di(t-amylperoxy)hexyne-3;-   2,5-dimethyl-2-t-butylperoxy-5-hydroperoxyhexane;-   2,5-dimethyl-2-cumylperoxy-5-hydroperoxy hexane;-   2,5-dimethyl-2-t-amylperoxy-5-hydroperoxyhexane;-   m/p-alpha, alpha-di[(t-butylperoxy)isopropyl]benzene;-   1,3,5-tris(t-butylperoxyisopropyl)benzene;-   1,3,5-tris(t-amylperoxyisopropyl)benzene;-   1,3,5-tris(cumylperoxyisopropyl)benzene;-   di[1,3-dimethyl-3-(t-butylperoxy)butyl]carbonate;-   di[1,3-dimethyl-3-(t-amylperoxy)butyl]carbonate;-   di[1,3-dimethyl-3-(cumylperoxy)butyl]carbonate;-   di-t-amyl peroxide;-   dicumyl peroxide;-   t-butylperoxy-meta-isopropenyl-cumyl peroxide;-   t-amyl cumyl peroxide;-   t-butyl-isopropenylcumylperoxide;-   2,4,6-tri(butylperoxy)-s-triazine;-   1,3,5-tri[1-(t-butylperoxy)-1-methylethyl]benzene-   1,3,5-tri-[(t-butylperoxy)-isopropyl]benzene;-   1,3-dimethyl-3-(t-butylperoxy)butanol;-   1,3-dimethyl-3-(t-amylperoxy)butanol; and mixtures thereof.

Other dialkylperoxides which may be used singly or in combination withthe other free radical initiators contemplated by the present disclosureare those selected from the group represented by the formula:

wherein R₄ and R₅ may independently be in the meta or para positions andare the same or different and are selected from hydrogen or straight orbranched chain alkyls of 1 to 6 carbon atoms. Dicumyl peroxide andisopropylcumyl cumyl peroxide are illustrative.

Other dialkyl peroxides include:

-   3-cumylperoxy-1,3-dimethylbutyl methacrylate;-   3-t-butylperoxy-1,3-dimethylbutyl methacrylate;-   3-t-amylperoxy-1,3-dimethylbutyl methacrylate;-   tri(1,3-dimethyl-3-t-butylperoxy butyloxy)vinyl silane;-   1,3-dimethyl-3-(t-butylperoxy)butyl    N-[1-{3-(1-methylethenyl)-phenyl} 1-methylethyl]carbamate;-   1,3-dimethyl-3-(t-amylperoxy)butyl    N-[1-{3(1-methylethenyl)-phenyl}-1-methylethyl]carbamate;-   1,3-dimethyl-3-(cumylperoxy))butyl    N-[1-{(3-(1-methylethenyl)-phenyl}-1-methylethyl]carbamate.

In the group of diperoxyketal initiators, the preferred initiatorsinclude:

-   1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;-   1,1-di(t-butylperoxy)cyclohexane;-   n-butyl 4,4-di(t-amylperoxy)valerate;-   ethyl 3,3-di(t-butylperoxy)butyrate;-   2,2-di(t-amylperoxy)propane;-   3,6,6,9,9-pentamethyl-3-ethoxycarbonylmethyl-1,2,4,5-tetraoxacyclononane;-   n-butyl-4,4-bis(t-butylperoxy)valerate;-   ethyl-3,3-di(t-amylperoxy)butyrate; and mixtures thereof.

Illustrative solid, room temperature stable peroxydicarbonates include,but are not limited to: di(2-phenoxyethyl)peroxydicarbonate;di(4-t-butyl-cyclohexyl)peroxydicarbonate; dimyristyl peroxydicarbonate;dibenzyl peroxydicarbonate; and di(isobornyl)peroxydicarbonate. Otherperoxides that may be used according to at least one embodiment of thepresent disclosure include benzoyl peroxide,OO-t-butyl-O-hydrogen-monoperoxy-succinate andOO-t-amyl-O-hydrogen-monoperoxy-succinate.

Illustrative cyclic ketone peroxides are compounds having the generalformulae (I), (II) and/or (III).

wherein R₁ to R₁₀ are independently selected from the group consistingof hydrogen, C1 to C20 alkyl, C3 to C20 cycloalkyl, C6 to C20 aryl, C7to C20 aralkyl and C7 to C20 alkaryl, which groups may include linear orbranched alkyl properties and each of R₁ to R₁₀ may be substituted withone or more groups selected from hydroxy, C1 to C20 alkoxy, linear orbranched C1 to C20 alkyl, C6 to C20 aryloxy, halogen, ester, carboxy,nitride and amido, such as, for example, at least 20% of the totalactive oxygen content of the peroxide mixture used for a crosslinkingreaction will be from compounds having formulas (I), (II) and/or (III).

Some examples of suitable cyclic ketone peroxides include:

3,6,9, triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (or methyl ethylketone peroxide cyclic trimer), methyl ethyl ketone peroxide cyclicdimer, and 3,3,6,6,9,9-hexamethyl-1,2,4,5-tetraoxacyclononane.

Illustrative examples of peroxy esters include:

-   2,5-dimethyl-2,5-di(benzoylperoxy)hexane;-   t-butylperbenzoate;-   t-butylperoxy acetate;-   t-butylperoxy-2-ethyl hexanoate;-   t-amyl perbenzoate;-   t-amyl peroxy acetate;-   t-butyl peroxy isobutyrate;-   3-hydroxy-1,1-dimethyl t-butyl peroxy-2-ethyl hexanoate;-   OO-t-amyl-O-hydrogen-monoperoxy succinate;-   OO-t-butyl-O-hydrogen-monoperoxy succinate;-   di-t-butyl diperoxyphthalate;-   t-butylperoxy (3,3,5-trimethylhexanoate);-   1,4-bis(t-butylperoxycarbo)cyclohexane;-   t-butylperoxy-3,5,5-trimethylhexanoate;-   t-butyl-peroxy-(cis-3-carboxy)propionate;-   allyl 3-methyl-3-t-butylperoxy butyrate.

Illustrative monoperoxy carbonates include:

-   OO-t-butyl-O-isopropylmonoperoxy carbonate;-   OO-t-butyl-O-(2-ethyl hexyl)monoperoxy carbonate;-   1,1,1-tris[2-(t-butylperoxy-carbonyloxy)ethoxymethyl]propane;-   1,1,1-tris[2-(t-amylperoxy-carbonyloxy)ethoxymethyl]propane;-   1,1,1-tris[2-(cumylperoxy-carbonyloxy)ethoxymethyl]propane;-   OO-t-amyl-O-isopropylmonoperoxy carbonate.

Illustrative diacyl peroxides include:

-   di(4-methylbenzoyl)peroxide;-   di(3-methylbenzoyl)peroxide;-   di(2-methylbenzoyl)peroxide;-   didecanoyl peroxide; dilauroyl peroxide;-   2,4-dibromo-benzoyl peroxide;-   succinic acid peroxide.-   dibenzoyl peroxide;-   di(2,4-dichloro-benzoyl)peroxide.

Imido peroxides of the type described in PCT Application publicationWO9703961 A1 6 Feb. 1997 are also contemplated as suitable for use andincorporated by reference herein.

Preferred peroxides include one or more of the following:2,5-di(t-butylperoxy)-2,5-dimethyl hexane; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;t-butylperoxy-isopropenylcumylperoxide; 3,3,5,7,7-pentamethyl,-1,2,4-trioxepane; 3,6,9,triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane;m/p-di(t-butylperoxy)diisopropyl benzene; m-di(t-butylperoxy)diisopropylbenzene; p-di(t-butylperoxy)diisopropyl benzene; di-t-butyl peroxide;di-t-amyl peroxide; dicumyl peroxide;1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-butylperoxy)valerate;ethyl 3,3-di(t-butylperoxy)butyrate; OO-t-butyl-O-(2-ethylhexyl)monoperoxy carbonate; OO-t-butyl-O-isopropylmonoperoxy carbonate;polyether poly-t-butylperoxy carbonate; t-butylperoxybenzoate;t-butylperoxyacetate; t-butylperoxymaleic acid;di(4-methylbenzoyl)peroxide; dibenzoyl peroxide;di(2,4-dichlorobenzoyl)peroxide; dilauroyl peroxide; cumenehydroperoxide; and di(4-tert-butylcyclohexyl)peroxydicarbonate.

More preferred peroxides include one or more of the following:2,5-di(t-butylperoxy)-2,5-dimethyl hexane; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;t-butylperoxy-isopropenylcumylperoxide; 3,3,5,7,7-pentamethyl,-1,2,4-trioxepane; 3,6,9,triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane;m/p-di(t-butylperoxy)diisopropyl benzene; m-di(t-butylperoxy)diisopropylbenzene; p-di(t-butylperoxy)diisopropyl benzene; di-t-butyl peroxide;dicumyl peroxide; 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-butylperoxy)valerate;ethyl 3,3-di(t-butylperoxy)butyrate; OO-t-butyl-O-(2-ethylhexyl)monoperoxy carbonate; OO-t-butyl-O-isopropylmonoperoxy carbonate;polyether poly-t-butylperoxy carbonate; t-butylperoxybenzoate; dibenzoylperoxide; di(2,4-dichlorobenzoyl)peroxide; cumene hydroperoxide; anddi(4-tert-butylcyclohexyl)peroxydicarbonate.

Even more preferred peroxides include one or more of the following:2,5-di(t-butylperoxy)-2,5-dimethyl hexane; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;t-butylperoxy-isopropenylcumylperoxide; 3,3,5,7,7-pentamethyl,-1,2,4-trioxepane; m/p-di(t-butylperoxy)diisopropyl benzene;m-di(t-butylperoxy)diisopropyl benzene; p-di(t-butylperoxy)diisopropylbenzene; di-t-butyl peroxide; dicumyl peroxide;1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-butylperoxy)valerate;ethyl 3,3-di(t-butylperoxy)butyrate; OO-t-butyl-O-(2-ethylhexyl)monoperoxy carbonate; OO-t-butyl-O-isopropylmonoperoxy carbonate;cumene hydroperoxide; t-butylperoxybenzoate; dibenzoyl peroxide; anddi(2,4-dichlorobenzoyl)peroxide.

Most preferred peroxides include one or more of the following:2,5-di(t-butylperoxy)-2,5-dimethyl hexane; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;t-butylperoxy-isopropenylcumylperoxide; m/p-di(t-butylperoxy)diisopropylbenzene; m-di(t-butylperoxy)diisopropyl benzene;p-di(t-butylperoxy)diisopropyl benzene; dicumyl peroxide; cumenehydroperoxide; 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di(t-butylperoxy)cyclohexane; n-butyl 4,4-di(t-butylperoxy)valerate;ethyl 3,3-di(t-butylperoxy)butyrate; OO-t-butyl-O-(2-ethylhexyl)monoperoxy carbonate; OO-t-butyl-O-isopropylmonoperoxy carbonate;and t-butylperoxybenzoate.

Examples of the nitroxide (or “nitroxide-containing compound”) mayinclude derivatives of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl),such as 4-hydroxy TEMPO (4-OHT) and 4-acetamido TEMPO. As used herein,the terms “quinone” or “quinone-containing compound” include bothquinones and hydroquinones, as well as ethers thereof such as monoalkyl,monoaryl, monoaralkyl and bis(hydroxyalkyl) ethers of hydroquinones.Non-limiting examples of quinones that may be used in formulations ofthe present invention include mono-tert-butylhydroquinone (MTBHQ),hydroquinone, hydroquinone mono-methyl ether (HQMME) (also known as4-methoxy phenol), mono-t-amylhydroquinone, hydroquinonebis(2-hydroxyethyl) ether, 4-ethoxy phenol, 4-phenoxy phenol,4-(benzyloxy) phenol, 2,5-bis (morpholinomethyl) hydroquinone, andbenzoquinone.

Preferred nitroxide-containing compounds include 4-hydroxy TEMPO (4-OHT)and TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl). Preferredquinone-containing compounds include mono-tert-butylhydroquinone(MTBHQ); hydroquinone; hydroquinone mono-methyl ether (HQMME) which isalso known as 4-methoxy phenol (MEHQ); mono-t-amylhydroquinone anddi-t-amyl hydroquinone.

In accordance with particular embodiments, organic peroxide formulationsof the present invention may further include at least one crosslinkingcoagent and/or at least one filler. According to particular embodiments,examples of crosslinking co-agents include allyl methacrylate, triallylcyanurate, triallyl isocyanurate, trimethyloylpropane trimethacrylate(SR-350®), trimethyloylpropane triacrylate (SR-351®), zinc diacrylate,and zinc dimethacrylate.

Additional non-limiting examples of crosslinking coagents include:Sartomer-manufactured methacrylate-type coagents, such as:

-   SR205H Triethylene glycol dimethacrylate (TiEGDMA),-   SR206H Ethylene glycol dimethacrylate (EGDMA),-   SR209 Tetraethylene glycol dimethacrylate (TTEGDMA),-   SR210HH Polyethylene glycol (200) dimethacrylate (PEG200DMA),-   SR214 1,4-butanediol dimethacrylate (BDDMA),-   SR231 Diethylene glycol dimethacrylate (DEGDMA),-   SR239A 1,6-hexanediol dimethacrylate (HDDMA),-   SR252 Polyethylene glycol (600) dimethacrylate (PEG600DMA),-   SR262 1,12-dodecanediol dimethacrylate (DDDDMA),-   SR297J 1,3-butylene glycol dimethacrylate (BGDMA),-   SR348C Ethoxylated 3 bisphenol A dimethacrylate (BPA3EODMA),-   SR348L Ethoxylated 2 bisphenol A dimethacrylate (BPA2EODMA),-   SR350D Trimethylolpropane trimethacrylate (TMPTMA),-   SR480 Ethoxylated 10 bisphenol A dimethacrylate (BPA10EODMA),-   SR540 Ethoxylated 4 bisphenol A dimethacrylate (BPA4EODMA),-   SR596 Alkoxylated pentaerythritol tetramethacrylate (PETMA),-   SR604 Polypropylene glycol monomethacrylate (PPGMA),-   SR834 Tricyclodecanedimethanol dimethacrylate (TCDDMDMA), and-   SR9054 Acidic difunctional adhesion promoter;    Sartomer-manufactured acrylate-type coagents, such as:-   SR238 1,6-hexanediol diacrylate (HDDA),-   SR259 Polyethylene glycol (200) diacrylate (PEG200DA),-   SR268G Tetraethylene glycol diacrylate (TTEGDA),-   SR272 Triethylene glycol diacrylate (TIEGDA),-   SR295 Pentaerythritol tetraacrylate (PETTA),-   SR306 Tripropylene glycol diacrylate (TPGDA),-   SR307 Polybutadiene diacrylate (PBDDA),-   SR341 3-methyl 1,5-pentanediol diacrylate (MPDA),-   SR344 Polyethylene glycol (400) diacrylate (PEG400DA),-   SR345 High performance high functional monomer,-   SR349 Ethoxylated 3 bisphenol A diacrylate (BPA3EODA),-   SR351 Trimethylolpropane triacrylate (TMPTA),-   SR355 Di-trimethylolpropane tetraacrylate (Di TMPTTA),-   SR368 Tris (2-hydroxyethyl) isocyanurate triacrylate (THEICTA),-   SR399 Dipentaerythritol pentaacrylate (Di PEPA),-   SR415 Ethoxylated (20) trimethylolpropane triacrylate (TMP20EOTA),-   SR444 Modified pentaerythritol triacrylate,-   SR444D Pentaerythritol triacrylate (PETIA),-   SR454 Ethoxylated 3 trimethylolpropane triacrylate (TMP3EOTA),-   SR492 Propoxylated 3 trimethylolpropane triacrylate (TMP3POTA),-   SR494 Ethoxylated 4 pentaerythritol tetraacrylate (PETTA),-   SR499 Ethoxylated 6 trimethylolpropane triacrylate (TMP6EOTA),-   SR502 Ethoxylated 9 trimethylolpropane triacrylate (TMP9EOTA),-   SR508 Dipropylene glycol diacrylate (DPGDA),-   SR534D Multifunctional acrylate specific for sulfur cure,-   SR595 1,10 decanediol diacrylate (DDDA),-   SR601E Ethoxylated 4 bisphenol A diacrylate (BPA4EODA),-   SR602 Ethoxylated 10 bisphenol A diacrylate (BPA10EODA),-   SR606A Esterdiol diacrylate (EDDA),-   SR610 Polyethylene glycol 600 diacrylate (PEG600DA),-   SR802 Alkoxylated diacrylate,-   SR833S Tricyclodecanedimethanol diacrylate (TCDDMDA),-   SR9003 Propoxylated 2 neopentyl glycol diacrylate (PONPGDA),-   SR9020 Propoxylated 3 glyceryl triacrylate (GPTA),-   SR9035 Ethoxylated 15 trimethylolpropane triacrylate (TMP15EOTA),    and-   SR9046 Ethoxylated 12 glyceryl triacrylate (G12EOTA);    Sartomer-manufactured Special Scorch Protected Type Coagents, such    as:-   Saret® 297F Liquid Scorch protected methacrylate,-   Saret® 350S Liquid Scorch protected methacrylate,-   Saret® 350W Liquid Scorch protected methacrylate,-   Saret® 500 Liquid Scorch protected methacrylate,-   Saret® 517 Liquid Scorch protected methacrylate, and-   Saret® 521 Liquid Scorch protected methacrylate;-   Cray Valley liquid high vinyl polybutadiene;-   liquid polybutadienes;-   Poly bd® and Krasol® series of hydroxyl terminated liquid    polybutadienes;-   Ricon Resins; e.g., Ricon® 154; Ricon® 156 MA17;

Functionalized liquid polybutadiene coagents such as:

-   diallyl functionalized polybutadienes,-   dimethacrylate functionalized polybutadienes,-   diacrylate functionalized polybutadienes    Allylic-type coagents, such as:-   Triallyl cyanurate (TAC),-   Triallyl isocyanurate (TAIC),-   Triallylphosphate (TAP),-   Triallyl borate (TAB),-   trimethallyl isocyanurate (TMAIC),-   Diallylterephthalate (DATP) aka diallyl phthalate,-   Diallyl carbonate,-   Diallyl maleate,-   Diallyl fumarate,-   Diallyl phosphite,-   Trimethylolpropane diallyl ether,-   Poly(diallyl isophthalate), and-   Glyoxal bis(diallyl acetal) (1,1,2,2-Tetraallyloxyethane);    Hybrid-type coagents, such as:-   Allyl methacrylate,-   Allyl acrylate,-   Allyl methacrylate oligomer,-   Allyl acrylate oligomer, and-   Sartomer SR523: New Dual Functional Coagent (an allyl methacrylate    or acrylate derivative);-   2,4-Diphenyl-4-methyl-1-pentene, also known as Nofmer MSD    (alpha-methylstyrene dimer) (available from Nofco, particularly for    wire and cable applications); and    miscellaneous other crosslinking coagents, such as:-   N,N′-m-phenylenedimaleimide, also known as HVA-2 (available from    DuPont),-   N,N′-p-phenylenedimaleimide,-   Cis-1,2-polybutadiene (1,2-BR),-   Divinylbenzene (DVB), and-   4,4′-(bismaleimide) diphenyl disulphide.

Preferred coagents include one or more of the following:2,4-diphenyl-4-methyl-1-pentene also known as Nofmer® MSD; divinylbenzene; triallyl cyanurate; triallyl isocyanurate; trimethallylisocyanurate; triallylphosphate; Sartomer's CN 9101 and CN 9102 tetraallyl urethane oligomers; diallyl maleate; diallyl fumarate; tetraallylpentaerythritol; pentaerythritol triallyl ether; trimethylolpropanetrimethacrylate; trimethylolpropane triacrylate; allyl methacrylateoligomer; 1,4-butanediol dimethacrylate; N,N′-m-phenylenedimaleimide;Sartomer SR-523 trimethylolpropane diallyl methacrylate; zincdiacrylate; zinc dimethacrylate; Saret® 297F; Saret® 350S; Saret® 350W;Saret® 500; Saret® 515; Saret® 516HP; Saret® 517HP; Saret® 519HP; Saret®521HP; Saret® 522; liquid high vinyl polybutadiene; liquidpolybutadiene; Poly bd® and Krasol® series of hydroxyl terminated liquidpolybutadienes; Ricon® Resins; e.g., Ricon® 154; and Ricon® 156 MA17.

Non-limiting examples of optional inert fillers for use in the organicperoxide formulations of the present invention include water washedclay, e.g., Burgess Clay, precipitated silica, precipitated calciumcarbonate, synthetic calcium silicate, and combinations thereof. Variouscombinations of these fillers can be used by one skilled in the art toachieve a free-flowing, non-caking final peroxide formulation.

In accordance with particular embodiments, the organic peroxideformulations of the present invention may include a silica filler.

The organic peroxide formulations of the present invention mayoptionally include at least one additive selected from the groupconsisting of process oils (e.g., aliphatic process oils), process aids,pigments, dyes, tackifiers, waxes, reinforcing aids, UV stabilizationagents, blowing agents, activators, antiozonants and coagents (e.g.,those marketed by Sartomer).

According to particular embodiments, the organic peroxide formulationcomprises, consists essentially of, or consists of:

between about 92 wt % and about 98 wt % organic peroxide(s),

between about 1 wt % and about 7 wt % nitroxide(s), and

between about 1 wt % and about 7 wt % quinone(s) (with the combinedtotal of nitroxide(s) and quinone(s) being between about 2 wt % andabout 8 wt %).

An additional embodiment of the present invention provides an elastomercomposition comprising, consisting essentially of, or consisting of:

-   -   at least one elastomer,    -   at least one organic peroxide,    -   at least one nitroxide-containing compound (e.g.,        4-hydroxy-TEMPO (4-OHT)), and    -   at least one quinone-containing compound (e.g.,        mono-tert-butylhydroquinone (MTBHQ)).

In at least one embodiment, the elastomer compositions of the presentinvention may comprise a saturated elastomer, an unsaturated elastomer,or a blend of both a saturated and unsaturated elastomer.

According to particular embodiments, the elastomer compositions of thepresent invention further comprise at least one polymer. The at leastone polymer of the elastomer composition may comprise a saturatedpolymer, an unsaturated polymer, or both a saturated and unsaturatedpolymer.

It should be noted that commercially-available pre-compounded elastomersmay be used in accordance with the present invention. These elastomersmay contain additives such as carbon black filler, process oils, moldrelease agents, antioxidants and/or heat stabilizers. According toparticular embodiments, the at least one elastomer is part of anelastomer masterbatch that includes one or more of these additives. Forexample, an elastomer masterbatch may comprise, consist essentially of,or consist of the at least one elastomer and one or more additivesselected from the group consisting of carbon black, polyethylene glycol,at least one process oil (e.g., liquid saturated hydrocarbons, such asPrimol® 352), at least one antioxidant (e.g.,2,2,4-trimethyl-1,2-dihydroquinoline, also referred to as TMQ), at leastone mold release agent, at least one heat stabilizer, and a combinationthereof.

As used herein, the term “polymer” means a non-elastomeric polymercomprised of at least at least one monomer in polymerized form. The term“polymer” encompasses homopolymers and copolymers, where the term“copolymers” refers to a polymer comprised of at least two differentmonomers in polymerized form. For example, a copolymer in accordancewith the present disclosure may be a polymer comprising two differentmonomers, a terpolymer is a polymer comprising three different monomersor more.

In at least one embodiment, the polymer of the elastomer compositioncomprises a copolymer. The embodiments disclosed herein recite elastomercompositions comprising a copolymer. However, as one of ordinary skillin the art would readily appreciate, a homopolymer may be substituted inany embodiment comprising a copolymer, unless expressly indicated to thecontrary.

In at least one embodiment, the elastomer composition comprises at leastone elastomer and at least one copolymer. The elastomer and copolymermay be present in the elastomer composition at weight ratios rangingfrom 99:1 to 1:99, such as, for example, from 85:15 to 15:85, or from75:25 to 25:75. In at least one embodiment, the elastomer and copolymerare present in the elastomer composition in a 50:50 weight ratio. Inanother embodiment, the elastomer composition includes 100% elastomer(s)and no copolymer(s).

According to at least one embodiment, the elastomer compositioncomprises at least one saturated elastomer. The saturated elastomer canbe selected from, for example, silicon rubber without unsaturation (Q),methyl-polysiloxane (MQ), phenyl-methyl-polysiloxane (PMQ),ethylene-vinyl acetate (EVA), high-density polyethylene (HDPE),low-density polyethylene (LDPE), chlorinated poly(ethylene) (CPE),poly(ethylene propylene) (EPM), fluoroelastomers (FKM, FFKM) (e.g.,Viton® and Dyneon®), and combinations thereof.

According to at least one embodiment, the elastomer compositioncomprises at least one unsaturated elastomer. Unsaturated elastomersthat may be used in the elastomer composition include, for example,ethylene-propylene-diene terpolymer (EPDM), vinyl silicone rubber (VMQ),fluorosilicone (FVMQ), nitrile rubber (NBR),acrylonitrile-butadiene-styrene (ABS), styrene butadiene rubber (SBR),styrene-butadiene-styrene block copolymers (SBS), polybutadiene rubber(BR), styrene-isoprene-styrene block copolymers (SIS), partiallyhydrogenated acrylonitrile butadiene (HNBR), natural rubber (NR),synthetic polyisoprene rubber (1R), neoprene rubber (CR),polychloropropene, bromobutyl rubber (BIIR), chlorobutyl rubber, andcombinations thereof.

In accordance with at least one embodiment, the elastomer compositioncomprises at least one saturated copolymer. Non-limiting examples ofsaturated polymers that may be used include copolymers of ethylene withpropylene, butylene, pentene, hexane, heptane, octane, and vinylacetate, such as, linear low density polyethylene (LLDPE), low densitypolyethylene (LDPE), poly(ethylene vinyl acetate) (EVA), poly(ethylenepropylene) (EPM), poly(ethylene octene) (e.g., Engage®), poly(ethylenehexene), poly(ethylene butylene) (e.g., Tafmer®), Vamac® polymers (e.g.,poly(ethylene methyl acrylate), poly(ethylene acrylate), andcombinations with acrylic acid), and combinations thereof.

Another embodiment of the present invention relates to a method formanufacturing an article comprising an elastomer composition asdescribed herein, wherein the method comprises curing the elastomercomposition.

As used herein, the term “curing” refers to the crosslinking of apolymer to form a strengthened or hardened polymer. A curing step may beperformed in any conventional manner.

The method may comprise extruding an elastomer composition, as describedherein, to form an uncured preform article, and curing the uncuredpreform article.

At least one embodiment of the present invention relates to a processfor curing an elastomer composition, wherein the composition comprises,consists essentially of, or consists of:

at least one elastomer,

at least one organic peroxide,

at least one nitroxide-containing compound (e.g., 4-hydroxy-TEMPO(4-OHT)), and

at least one quinone-containing compound (e.g.,mono-tert-butylhydroquinone (MTBHQ)). The process may further comprisemixing the components separately or together, and in any order, toprovide the elastomer composition.

In at least one embodiment, one or more conventional additives such asantioxidants (e.g., hindered phenols and polymeric quinolinederivatives), aliphatic process oils, process aids, pigments, dyes,tackifiers, waxes, reinforcing aids, UV stabilization agents, blowingagents, scorch protectors, activators, antiozonants or coagents may alsobe added to any of the elastomer compositions described herein before,after and/or during the curing step.

Non-limiting examples of applications for the peroxide formulations ofthe present invention include the use of liquid and filler-extendedgrades of the organic peroxides for crosslinked HDPE rotational molding;PEX-a pipe production; injection molded, compression molded, transfermolded crosslinked goods; wire and cable; general crosslinkedelastomers, rubber and polymers; modification of polymer molecularweight and grafting of agents such as maleic anhydride (MAH) andglycidyl methacrylate; dynamic vulcanization for production of TPV(thermoplastic vulcanizates); and crosslinked rubber or polymer foams.

The embodiments described herein are intended to be exemplary of theinvention and not limitations thereof. One skilled in the art willappreciate that modifications to the embodiments and examples of thepresent disclosure may be made without departing the scope of thepresent disclosure. The embodiments of the invention are described aboveusing the term “comprising” and variations thereof.

However, it is the intent of the inventors that the term “comprising”may be substituted in any of the embodiments described herein with“consisting of” and “consisting essentially of” without departing thescope of the invention. The invention further includes the followingembodiments

-   -   1. An organic peroxide formulation comprising:        -   at least one organic peroxide,        -   at least one nitroxide-containing compound, and        -   at least one quinone-containing compound.    -   2. The organic peroxide formulation of claim 1, wherein the at        least one nitroxide-containing compound comprises 4-OHT.    -   3. The organic peroxide formulation of any of claim 1, wherein        the at least one nitroxide-containing compound is at least one        or more of the following: 4-hydroxy TEMPO (4-OHT) and TEMPO        (2,2,6,6-tetramethylpiperidine 1-oxyl).    -   4. The organic peroxide formulation of any of claims 1 to 3,        wherein the at least one quinone-containing compound comprises        MTBHQ.    -   5. The organic peroxide formulation of any of claims 1 to 4,        wherein the at least quinone-containing compound comprises        HQMME.    -   6. The organic peroxide formulation of any of claims 1 to 3,        wherein the at least one quinone-containing compound is at least        one or more of the following: mono-tert-butylhydroquinone        (MTBHQ); hydroquinone; hydroquinone mono-methyl ether (HQMME);        mono-t-amylhydroquinone and di-t-amyl hydroquinone.    -   7. The organic peroxide formulation of any of claims 1 to 6,        further comprising at least one crosslinking coagent comprising        a moiety having at least two functional groups, wherein said        functional groups are selected from the groups consisting of        allylic, methacrylic, acrylic and may be the same or different.    -   8. The organic peroxide formulation of any of claims 1 to 7,        wherein the at least one peroxide comprises one or more of a        dialkyl, peroxyketal, peroxyester, monoperoxycarbonate or        hydroperoxide type peroxide.    -   9. A method for manufacturing the organic peroxide formulation        of claim 1 comprising mixing the at least one organic peroxide,        the at least one nitroxide-containing compound, and the at least        one quinone-containing compound.    -   10. An elastomer composition of any of claims 1 to 9 comprising:        -   at least one elastomer,        -   at least one organic peroxide,        -   at least one nitroxide-containing compound, and        -   at least one quinone-containing compound.    -   11. A process for curing an elastomer composition of any of        claims 1 to 10, said process comprising:        -   curing an elastomer composition in the presence of oxygen,        -   wherein the elastomer composition comprises at least one            elastomer, at least one organic peroxide, at least one            nitroxide-containing compound, and at least one            quinone-containing compound.    -   12. An elastomeric article manufactured according to the method        of claim 11.    -   13. An organic peroxide formulation comprising:        -   at least one organic peroxide,        -   at least one nitroxide-containing compound, and        -   at least one quinone-containing compound.        -   at least one crosslinking coagent    -   14. The organic peroxide formulation of claim 13, wherein the at        least one crosslinking coagent comprises a moiety having at        least two functional groups, wherein said functional groups are        selected from the groups consisting of allylic, methacrylic,        acrylic and may be the same or different.    -   15. The organic peroxide formulation of claim 13, wherein the at        least one crosslinking coagent comprises        2,4-diphenyl-4-methyl-1-pentene and optionally one of the        coagents recited in claim 14.    -   16. The organic peroxide formulation of any of claims 13 to 15,        wherein the at least one peroxide is more or more peroxide        selected from the group consisting of dialkyl, peroxyketal,        peroxyester, monoperoxycarbonate or hydroperoxide type peroxide.

Within this specification embodiments have bee described in a way whichenables a clear and concise specification to be written, but it isintended and will be appreciated that embodiments may be variouslycombined or separated without parting from the invention. For example,it will be appreciated that all preferred features described herein areapplicable to all aspects of the invention described herein.

The following examples further illustrate the best mode contemplated bythe inventors for the practice of their invention and are to beconstrued as illustrative and not in limitation thereof.

EXAMPLES Abbreviations Used in the Examples

MH (dN-m)=Maximum torque achieved in deci-Newton-meters; relates tocrosslinking attained.

ML (dN-m)=Minimum torque in dN-m.

Ts0.4 (min)=Time in minutes to achieve a 0.4 dN-m increase from minimumtorque.

Ts1.0 (min)=Time in minutes to achieve a 1.0 dN-m increase from minimumtorque.

Ts2.0 (min)=Time in minutes to achieve a 2.0 dN-m increase from minimumtorque

Tc90 (min)=Time in minutes to achieve 90% of the total cure time.

Luperox® F=m/p-di(t-butylperoxy)diisopropylbenzene (a meltable solidperoxide).

Luperox® IP-D16=t-butylperoxy-isopropenylcumylperoxide (a liquidperoxide).

Luperox® D-16=t-butyl cumylperoxide (a liquid peroxide).

Luperox® TBEC=OO-t-butylperoxy-O-(2-ethylhexyl)monoperoxycarbonate.4-OHT=4-Hydroxy TEMPO also known as4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl.

HDPE=high density polyethylene

HQMME=hydroquinone mono-methyl ether; also known as 4-methoxy phenol(MEHQ)

MTBHQ=mono-tertiary-butyl-hydroquinone, CAS 1948-33-0.

TAC=triallyl cyanurate (a crosslinking coagent).

EVA=poly(ethylene vinylacetate).

Example 1

Crosslinking a polyethylene polymer, in this case HDPE (High DensityPolyethylene), resulted in longer scorch times when using thesynergistic combination of 4-OHT and MTBHQ. This blend, shown in TABLE 1as OP-B, used less overall additive in the peroxide formulation, whileproviding significantly longer scorch time values for cure andcompounding temperatures.Efficiency=[(MH−ML)×Ts]÷(Tc90−Ts),wherein a higher Efficiency value indicates a higher efficiency ofscorch time with respect to the various additives' effect on the amountof crosslinking obtained and the cure time achieved for the peroxideformulation.

The synergy of 4-OHT and MTBHQ makes it possible to produce homogeneousliquid and meltable solid peroxide compositions for applications andprocesses that cannot normally tolerate fillers.

TABLE 1 Peroxide Formulations OP-A OP-B OP-C OP-D OP-E OP-F OrganicPeroxide Formulations Luperox ® 0.0% 0.0% 48.7% 48.4% 46.0% 46.7% IP-D16Luperox ® F 92.0% 93.4% 48.7% 48.4% 46.0% 46.7% 4-OHT 8.0% 4.0% 0.0%0.0% 8.0% 4.0% MTBHQ 0.0% 2.6% 2.6% 3.2% 0.0% 2.6% Total 100.0% 100.0%100.0% 100.0% 100.0% 100.0% Crosslinking HDPE HDPE parts 100 100 100 100100 100 OP-A parts 1.1 — — — — — OP-B parts — 1.1 — — — — OP-C parts — —1.1 — — — OP-D parts — — — 1.1 — — QP-E parts — — — — 1.1 — OP-F parts —— — — — 1.1 RPA Rheometer Cure Data @190° C., 1 deg arc, 100 cpm forHDPE MH − ML 10.2 10.1 10.14 10.17 10.13 10.2 (dN-m) Ts0.4 (min) 0.840.90 0.88 0.83 0.90 0.95 Tc90 (min) 3.30 3.35 3.5 3.63 3.42 3.53Efficiency 3.48 3.71 3.53 3.01 3.62 3.76 RPA Rheometer Compounding Data@162° C., 1 deg arc, 100 cpm for HDPE Ts0.4 (min) 6.80 7.5 6.7 6.32 8.178.33 Ts1.0 (min) 8.42 9.87 9.85 9.48 10.96 11.80

TABLE 1 compares the singular use of 8.0% 4-OHT in OP-A to the OP-Bperoxide blend of the present invention, which comprises a blend of 4.0%4-OHT and 2.6% MTBHQ. This blend of additives required only 6.6% versus8.0% of 4-OHT in OP-A, while producing a considerably desirable longerscorch time protection (Ts0.4 and Ts1.0) when crosslinking the HDPEpolymer at 190° C. and also at the 162° C. compounding temperature.

TABLE 1 also shows organic peroxide formulations OP-C, OP-D, OP-E andOP-F, which all use a 50:50 blend of two different peroxides, IP-D16 andLuperox® F. The IP-D16 is a higher half-life peroxide compared toLuperox® F, so it is slower in its rate of decomposition at a giventemperature and will improve scorch time and increase cure time.

Using 2.6% MTBHQ in combination with 4% 4-OHT for a total of 6.6%additives in formulation OP-F provided significantly longer (Ts0.4 andTs1.0) scorch times at 190° C. and 162° C. compared to the singular useof additives at equal to higher loadings, as shown for OP-C, OP-D andOP-E in TABLE 1.

Example 2

As shown in TABLE 2, the blend of 4-OHT and MTBHQ was compared to thesingular use of 4-OHT along with a crosslinking coagent TAC (triallylcyanurate). The blend in accordance with the invention, OP-H, provided ahigher Efficiency calculation with respect to increased scorch time whencrosslinking HDPE. The total weight of the synergistic blend was only6.7% versus 8% for the single additive usage.

TABLE 2 Peroxide Formulations OP-G OP-H Organic Peroxide FormulationsLuperox ® F 36.0% 36.5% TAC 56.0% 56.8% 4-OHT 8.0% 4.1% MTBHQ 0.0% 2.6%Total 100.0% 100.0% Crosslinking HDPE HDPE parts 100 100 OP-F parts 1.1— OP-G parts — 1.1 RPA Rheometer Cure Data @190° C., 1 deg arc, 100 cpmfor HDPE MH − ML (dN-m) 10.24 10.25 Ts0.4 (min) 0.82 0.86 Tc90 (min)2.89 3.00 Efficiency 4.05 4.12

Example 3

As shown in TABLE 3, the components of the organic peroxide formulationswere compared on an equal weight basis for the crosslinking of EVA at170° C. using the organic peroxide Luperox® D-16 (a liquid organicperoxide whose chemical name is t-butylcumylperoxide). The blend inaccordance with the present invention in TABLE 3, OP-J, provided thebest combination of crosslinking based on MH—ML (dN-m), plus the longestTs1 and Ts2 (min) scorch times. The Tc90 time also increased, but basedon the Efficiency calculations the increase in scorch time and goodcrosslinking performance more than made up for the increase in curetime. Good Efficiencies were obtained for the synergistic blend for bothTs1 and Ts2 values, surpassing the performance obtained by the equalweight usage of 4-OHT and MTBHQ in OP-I and OP-K respectively. The OP-Kprovided the highest scorch time values, but the MH—ML (dN-m) valueswere severely lowered, which significantly lowered the scorch Efficiencyvalue, as shown in TABLE 3. Higher calculated scorch time Efficiencyvalues are preferred.

TABLE 3 Crosslinking EVA Parts of EVA 100 100 100 Peroxide FormulationsOP-I OP-J OP-K Parts of Luperox ® D16 1.5 1.5 1.5 Parts of 4-OHT 0.4 0.20.0 Parts of MTBHQ 0.0 0.2 0.4 RPA Rheometer Cure Data @170° C., 1 degarc, 100 cpm for EVA MH − ML (dN-m) 10.56 11.15 7.47 Ts1 (min) 1.16 1.662.08 Ts2 (min) 1.32 1.95 2.71 Tc90 (min) 5.11 6.63 8.09 Efficiency basedon Ts1 3.10 3.72 2.59 Efficiency based on Ts2 3.68 4.65 3.76

Example 4

In Example 4 the synergistic benefit of using a blend of HQMME and 4-OHTin Run #3 is demonstrated; TABLE 4 for crosslinking EVA with amonoperoxycarbonate, e.g.,OO-t-butylperoxy-O-(2-ethylhexyl)monoperoxycarbonate. The peroxide is amonoperoxycarbonate. The trade-name ofOO-t-butylperoxy-O-(2-ethylhexyl)monoperoxycarbonate is Luperox® TBEC.

The combination of HQMME and 4-OHT provided a good crosslinking,increased Ts1 and Ts2 scorch time and provide an unexpectedly shortercure time (based on Tc90 min), compared to Run #1 and #2 which useeither HQMME or 4-OHT, but not in combination.

TABLE 4 Run # 1 2 3 EVA 100.000 100.000 100.000 Luperox ® TBEC 0.6080.686 0.686 HQMME 0.041 — 0.046 TAC (triallyl cyanurate) 0.162 0.1830.183 4-OHT — 0.110 0.259 Crosslinking EVA: RPA cure at 160 C., 0.5 degarc, 100 cpm MH (dN-m) 29.49 27.864 22.234 ML (dN-m) 12.089 11.64711.685 Ts1 (min) 0.34 0.33 0.39 Ts2 (min) 0.45 0.44 0.56 Tc90 (min)14.13 16.67 5.31 Efficiency based on Ts1 (min) 0.43 0.33 0.84 Efficiencybased on Ts2 (min) 0.55 0.33 1.86

The unexpected synergy using 4-OHT and MTBHQ when blended with Luperox®TBEC makes it possible to provide an unexpected good crosslinking withlonger Ts1 and Ts2 scorch times and a substantially shorter cure time(based on Tc90) thus improving overall productivity, as demonstrated bythe Efficiency equation. TAC (triallyl cyanurate) a crosslinking coagentwas also used in all of the peroxide formulations in Example 4.

Efficiency Equation

Efficiency=[(MH−ML)×Ts]÷(Tc90−Ts)

A higher Efficiency value may indicate a higher efficiency of scorchtime and cure time taking into account crosslinking. The equation helpsto compare the benefits of the final peroxide formulation. A longerscorch time is desired, but not at the expense of a substantially longercure time. If one can substantially decrease cure time, whilemaintaining or increasing scorch time, that is preferred. The novelblend of HQMME and 4-OHT provided improved overall crosslinkingefficiency as demonstrated by the determination obtained from the“Efficiency equation”.

What is claimed is:
 1. A liquid or meltable solid organic peroxideformulation for curing solid elastomer compositions in the presence ofoxygen, said formulation consisting of a homogeneous blend of: at leastone organic peroxide, at least one nitroxide-containing compound whichis at least one or more of the following: 4-hydroxy TEMPO (4-OHT) andTEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl), and at least onequinone-containing compound which is at least one or more of thefollowing: mono-tert-butylhydroquinone (MTBHQ); hydroquinone;hydroquinone mono-methyl ether (HQMME); mono-t-amylhydroquinone anddi-t-amyl hydroquinone, optionally one or more of the following: inertfiller, process oils, process aids, pigments, dyes, tackifiers, waxes,reinforcing aids, UV stabilization agents, blowing agents, activators,antiozonants and coagents, wherein said solid organic peroxideformulation is liquid or meltable and cures said solid elastomers. 2.The liquid or meltable solid organic peroxide formulation of claim 1,wherein the at least one nitroxide-containing compound comprises 4-OHT.3. The liquid or meltable solid organic peroxide formulation of claim 1,wherein the at least one nitroxide-containing compound is TEMPO(2,2,6,6-tetramethylpiperidine 1-oxyl).
 4. The liquid or meltable solidorganic peroxide formulation of claim 1, wherein the at least onequinone-containing compound comprises MTBHQ.
 5. The liquid or meltablesolid organic peroxide formulation of claim 1, wherein the at least onequinone-containing compound comprises HQMME.
 6. The liquid or meltablesolid organic peroxide formulation of claim 1, wherein the at least oneperoxide comprises one or more of a dialkyl, peroxyketal, peroxyester,monoperoxycarbonate or hydroperoxide peroxides.
 7. The liquid ormeltable solid organic peroxide formulation of claim 1 wherein saidliquid or meltable solid organic peroxide formulation is sprayable. 8.The liquid or meltable solid organic peroxide formulation of claim 6which is sprayed onto inert filler.
 9. A method for manufacturing theorganic peroxide formulation of claim 1 comprising mixing the at leastone organic peroxide, the at least one nitroxide-containing compound,and the at least one quinone-containing compound.
 10. An elastomercomposition comprising: at least one solid elastomer, and the liquid ormeltable solid organic peroxide formulation of claim
 1. 11. A processfor curing an elastomer composition in the presence of oxygen, saidprocess comprising: curing an elastomer composition in the presence ofoxygen, wherein the elastomer composition comprises at least one solidelastomer, and the liquid or meltable solid organic peroxide formulationof claim
 1. 12. An elastomeric article manufactured according to themethod of claim
 11. 13. A liquid or meltable solid organic peroxideformulation for curing a solid elastomer composition, said formulationconsisting of a homogeneous blend of: at least one organic peroxide, atleast one nitroxide-containing compound which is 4-hydroxy TEMPO(4-OHT), at least one quinone-containing compound which is at least oneor more of the following: mono-tert-butylhydroquinone (MTBHQ);hydroquinone; hydroquinone mono-methyl ether (HQMME);mono-t-amylhydroquinone and di-t-amyl hydroquinone, and at least onecrosslinking coagent comprising a moiety having at least two functionalgroups, wherein said functional groups are selected from the groupsconsisting of allylic, methacrylic, acrylic and may be the same ordifferent, and optionally one or more of the following: inert filler,process oils, process aids, pigments, dyes, tackifiers, waxes,reinforcing aids, UV stabilization agents, blowing agents, activators,antiozonants and coagents.
 14. The liquid or meltable solid organicperoxide formulation of claim 13, wherein the at least one peroxide isone or more peroxide selected from the group consisting of dialkyl,peroxyketal, peroxyester, monoperoxycarbonate or hydroperoxideperoxides.
 15. The liquid or meltable solid organic peroxide formulationof claim 13 wherein said liquid or meltable solid organic peroxideformulation is sprayable.
 16. The liquid or meltable solid organicperoxide formulation of claim 13 which is sprayed onto inert filler.